1. Field of the Invention
The present invention relates generally to a display module, and more particularly, to an EMR (ElectroMagnetic Resonance) type digitizer-integrated display module.
2. Description of the Related Art
An LCD (Liquid Crystal Display) module is adapted to display desired images by controlling a light transmissivity of each of liquid crystal cells arranged in a matrix form in accordance with image signal information.
An LCD module may be equipped with a digitizer for inputting an electric graphic signal while simultaneously displaying an image. The LCD module equipped with such a digitizer is often employed in such devices as a personal portable terminal, an all-in-one PC (Personal Computer), a tablet PC, a smart phone, or a PMP (Portable Multimedia Player). Unlike an input device, such as a mouse or a keyboard, the digitizer receives information concerning one or more positions designated by a user on a screen. As a result, the digitizer is suitable for conducting graphic work such as a CAD (Computer Aided Design), and is frequently used to provide an intuitive and convenient user interface.
Such a digitizer is also referred to as touch screen or EGIP (Electric Graphic Input Panel), and is classified into a resistive, capacitive, EMR (ElectroMagnetic Resonance) or electromagnetic type in accordance with the manner in which the digtizer detects one or more positions designated by the user.
The resistive type digitizer senses one or more positions pushed by pressure on the basis of a change in amount of current in a state in which a Direct Current (DC) voltage is applied to the digitizer, in which two thin conductive layers on a screen sense that they are directly touched on the basis of pressure by a finger or a stylus pen. Since the resistive type senses the positions on the basis of pressure, the conductance of the object to be sensed is immaterial.
The capacitive type digitizer senses one or more positions using capacitance coupling in a state in which an Alternating Current (AC) voltage is applied to the digitizer, in which the object to be sensed should be a conductor, and a contact area not less than a predetermined extent is needed so as to change the sensible electrostatic capacitance. Although, such a capacitive type digitizer does not have a problem in sensing a position when inputting is conducted using a human finger, this digitizer has difficulty sensing a position when inputting is conducted using a conductor tip since due to the small size of the contact area of the conductive tip.
Meanwhile, the electromagnetic resonance type digitizer employs a digitizer sensor substrate including a plurality of coils, and is driven by AC signals so that a pen produces a vibrating magnetic field when a user moves the pen. The vibrating magnetic field induces signals in the coils, through which signals the electromagnetic resonance type digitizer detects the position of the pen.
FIG. 1 illustrates an operating principal of a conventional electromagnetic type digitizer. As shown in FIG. 1, the electromagnetic type digitizer has a plurality of antenna coils 133 patterned on a digitizer sensor substrate 131, and is adapted to detect the position of a pen 117 by sensing a signal produced from a resonance circuit 117a provided within the pen 117. The sensed signal 137 passes a signal reception circuit 139 by which the position of the pen is recognized.
In this manner, the electromagnetic type digitizer has plural coils mounted on the digitizer substrate, and senses an electromagnetic change caused by the approach of the pen to determine the position of the pen. Therefore, unlike a resistive type digitizer, the electromagnetic digitizer does not need to be arranged on the front side of a display module, but may instead be mounted on the rear side of the display module.
FIG. 2 illustrates a display which is equipped with a conventional digitizer. Referring to FIG. 2, the display with a conventional digitizer has an LCD module including a liquid crystal panel 10 having a front polarizer 13, a thin film transistor substrate 11, a color filter substrate 12, and a rear polarizer, a backlight assembly having optical sheets 21, a light guide plate 22, a reflecting sheet 23, and a lamp unit 24, a mold frame 30 supporting the liquid crystal panel 10 and the backlight assembly 20, and a metal bracket 40 enclosing the periphery of the mold frame 30, and in which a digitizer module 50 is positioned under the LCD module, the digitizer module 50 including an EMR sensor substrate 51, a magnetic sheet 52 and an electromagnetic shield substrate 53.
The liquid crystal panel 10 has a plurality of liquid crystal cells arranged in a matrix form, and each of which forms a pixel unit. The liquid crystal panel 10 forms an image by controlling the light transmissivity of each of the liquid crystal cells in accordance with image signal information transmitted from a controller (not shown).
The backlight assembly 20 includes a light guide plate 22 arranged parallel to the rear side of the liquid crystal panel 10, a lamp unit 24 arranged along at least one side edge of the light guide plate 22 to supply light, optical sheets 21 provided on the front side of the light guide plate 22 to diffuse and concentrate light directed toward the liquid panel 10, and a reflecting sheet 23 provided on the rear side of the light guide plate 22.
In such a conventional digitizer-integrated display module, a metallic structure, which interferes with an electromagnetic field produced from the EMR sensor substrate 51, does not exist between the LCD module and the EMR sensor substrate 51. Therefore, a robust design of a display module should be conducted through an application of a frame on the periphery of the display module, and an electromagnetic shield substrate 53 should be provided under the EMR sensor substrate 51, in which the electromagnetic shield substrate prevents electromagnetic interference with a main board arranged under the digitizer module 50.
Thinning of an electronic appliance has become an important issue when developing such an electronic appliance. As a result, securing the rigidity of a display module with a minimal thickness and a minimal Bezel area has become a core technology in developing a display and a display set. However, the conventional digitizer-integrated display requires a wide Bezel area due to the side metal bracket structure, and is limited as to rigidity in the entire module due to the non-existence of a metal structure under the LCD module. In order to compensate for this deficiency, a thicker and highly rigid side frame and mold frame are required, which will inevitably increase the Bezel width and the thickness of the entire display module.
In order to avoid the interference of the EMR sensor substrate 51 with an internal circuit positioned below the EMR sensor substrate 51, one or more additional parts, such as the electromagnetic shield substrate 53, are required, which will inevitably cause an increase of the Bezel width and the thickness of the entire display module. Even if an additional part is used as shown in FIG. 2, it is difficult to shield the periphery of the EMR sensor substrate 51. As a result, interference occurs between the main board and the EMR sensor substrate 51, which may cause a malfunction of the digitizer or communication function.
As a result, there is a need in the art for a digitizer-integrated display module which is configured with a narrow Bezel while securing the rigidity of the display, and of which the thickness is not substantially increased.